Failing to do enough to stop money flowing to Hamas is not the same as creating Hamas or "propping it up."

Hostile borders can only be defended by depth - minefields, ditches, dragons teeth and other obstacle and hidden firing points (that can't be observed by the enemy) - See Russian defences in Ukraine. Israel tried to do the impossible and defend a border with no depth because it was politically difficult to create a buffer zone in Gaza (the correct choice) or in Israel (a defeat by loss of productive land).

Israel is now remedying this situation with a 1km buffer zone inside Gaza.
This is a small start in re-establishing the basis of Israeli deterrence - Attack us and you will lose your land.
Its the only thing Islamists understand.